Without a lot of detail, I'm having some power issues. Current cam has around .710 lift. One of the issues I think I have is controlling my valvetrain from 4000 to 8000 rpm. I just pulled the motor back out to put on the engine dyno to do some investigating, but spring pressure seems to be a possible culprit in my power loss. What kind of pressures, on the seat and open, are you guys running? If you're not sure, just state brand and spring number, and I can go from there. Thanks in advance

 

How much dur.@ .050"? You want around 275-300 seat & 575-600 open. On a real nasty cam cam w/ more lift and duration (.750"+) 400-410 seat & 950.lbs open.

 

280/286 @ .050". That's more pressure than I'm running now for sure. Thanks for the reply Bryan. With my current intake port, I am limited to a 1.43" spring. Is there one out there that O.D. that can suit my needs?

 

Just a few questions:

What is your valvestem diameter?

What series of lobes are you using?

What are your current valvesprings (brand, part #, installed height,etc.)?

Jason

 

Valvestem dia. is stock 8mm.
The lobes are custom (not comp, crane, or lunati)
Right now I'm using some Ferrea drop-in solid roller springs. Stock diameter.
180 lbs on the seat, and 480 open at 1.850" installed height.
I have some Comp 999s, but can't use them on these heads. I haven't spring checked those, but I believe it's 250 or so on the seat, and 670 open.

 

Most of the SR stuff we do is 210-230 on the seat and about 500 open with a 660 lift cam.

Whats the length of the valve Ryan? +.070? +.100? Stock?

What rockers?

Lash Cold/Hot?

Iron block?

What lifter/pushrod- Know the weights?

Lets do some thinking before we throw 400 on the seat at it. This isnt a bigblock trying to control a 2.2 massive stem valve

 

.100 long Louis. I'm using the T&Ds, and have a cold lash of .026. I didn't measure the lifter or pushrod weights before installation, but it's an 8.000" rod, and the new Comp LS1 link bar type solids.
Even if my pressure was way down (which I think it is), could that possibly account for a loss of 150 hp?

 

UGGG! Tighten that cold lash up!! It'll grow atleast .010 when it warms up, you'll kick a pushrod out real quick if you don't.

I'm just under .700 on the lift side, but much less duration. Isky spring, don't have the part number handy here. We changed it from a Comp 935 to get more seat and open pressure.

5/16" intake valve stem, 11/32" exhaust valve, install height is 1.900 if memory serves. T&D rockers, new comp lifters, 7.925 pushrod.

Spins clean to 8k

 

I think I'm going with 999s, I have no idea what was on these heads when I bought them but they are dropping under 180 right now on the seat and it is definately starting to lose power above 7200.

With my cam I'm going to go ~225 on the seat, I have crane lifters, 11/32 intake and exh valves, T&Ds and 5/16 7.4" pusrods.

 

If it is float, you bet.

got a graph?

26 cold is a lot. If thats an iron block, its no sobad , but for an aluminum block motor, thats waaaay to much.

you obviously cant weigh your valvetrain now, put it on the dyno and have a look.

Get a pull type, on car valvespring checker and see where they are at.

Has you lash changed much from the last time you checked it?

Are there any inconsistencies in the lash from rocker to rocker?

Whats the oil fliter look like?

Thats all for now

 

Iron block motor. I had the lash high to bring in some more cylinder pressure. We ran it at .030", and it worked, but backed it off a little.
UPDATE- Pulled the motor last night. Found the culprit. Weak springs alright. Intake ports were cooked from too much valve bounce. Time to put on the 999s

 

Good Choice, thats what I am going with Comp 999's

 

What were their measurements?